1. Technical Field
The present invention relates to optical elements, and more particularly, the present invention relates to optical elements that include a surface-emitting type semiconductor laser and a light-receiving element that detects a part of laser light emitted from the surface-emitting type semiconductor laser.
2. Related Art
Surface-emitting type semiconductor lasers have a characteristic in that their optical output changes according to the surrounding temperature, and therefore a surface-emitting type semiconductor laser may be provided with a light-receiving element having an optical detection function for monitoring its light output value. However, it is difficult to control the plane of polarization in such an optical element equipped with a surface-emitting type semiconductor laser and a light-receiving element. For this reason, when the surface-emitting type semiconductor laser is used in an optical system having polarization-dependency, noise may be generated because its plane of polarization is unstable.
In this respect, methods for controlling the plane of polarization for a surface-emitting type semiconductor laser have been proposed. For example, JP-A-11-307882 proposes a method for controlling the plane of polarization in which an oxidized layer for current constriction and an oxidized layer (anisotropic configuration) for adding stress are provided adjacent to an active layer, and strong stress is applied to the active layer while maintaining the energy use efficiency. However, in this case, the oxidized layer structure near the active layer and oxidation steps are complex and the element service life may be adversely affected.
Further, because a surface-emitting type semiconductor laser has a characteristic in that its optical output changes according to the surrounding temperature, the surface-emitting type semiconductor laser may be provided thereon with a light-receiving element having an optical detection function for monitoring its light output value. However, it is difficult to control the plane of polarization in such a surface-emitting type semiconductor laser equipped with a light-receiving element as it is influenced by light reflected by the light-receiving element. Therefore, the plane of polarization becomes unstable even when the polarization control structure described in JP-A-11-307882 is used. For this reason, when the surface-emitting type semiconductor laser is used in an optical system having polarization-dependency, noise may be generated because its plane of polarization is unstable.